CN1650808A - A Method for Measuring Fault Locations Using Statistical Image Planning Tomography - Google Patents

Abstract

The invention relates to a statistical graph planning method of fault position in tomographic image measurement. Among the methods and computer program products to operate tomography devices, standard measurement record is produced by displaying the design description of standard object, defining the space position of standard imaging region in the design description and storage; the standard measurement record is produced as the reference to the standard measurement record as the standard object, the standard object of the standard imaging region and parameters; by obtaining the data expressing the characteristics of inspection object corresponding to the standard object, the geometric relation between the characteristics of inspection object and the characteristics of standard object is determined, and a measurement record specialized on objects is produced, wherein by modifying standard measurement record with respect to the positioning imaging region of inspection object, the standard measurement record is then used to fault position planning of actual tomography measurement.

Description

A Method for Measuring Fault Locations Using Statistical Image Planning Tomography

technical field

The invention relates to a method for planning fault positions for tomographic (magnetic resonance) measurements, including recording of operating magnetic resonance imaging devices.

Background technique

Magnetic resonance imaging (MRI, also known as magnetic resonance tomography (MRT)) is a physical phenomenon based on nuclear magnetic resonance, which has been successfully used in clinical and biomedical fields as an imaging modality for more than 15 years. In this form of imaging, an object, such as a living patient, is placed in a strong, constant magnetic field. As a result, the spins of the previously irregularly oriented nuclei in this object are aligned into alignment. Radiofrequency energy is emitted into the object, exciting these "regular" nuclear spins to a specific resonance. This resonance generates the actual measurement signal, which is picked up by a suitable receiving coil. By applying inhomogeneous magnetic fields (gradient magnetic fields) generated by gradient coils, the signals received from the examination object can be spatially encoded in all three spatial directions. The section of the examination object used for imaging can be selected arbitrarily, thus allowing tomographic images of the human body to be obtained in all directions. Magnetic resonance imaging, as a tomographic method for medical diagnostic purposes, is primarily considered a "non-invasive" examination technique with universal contrast capabilities. Magnetic resonance imaging has been developed as an imaging modality that is often superior to X-ray computed tomography (CT) due to its excellent representation of soft tissues. Current magnetic resonance imaging is based on spin-echo and gradient-echo sequences which make it possible to obtain excellent image quality with measurement times of the order of minutes.

Each time a subject is examined (scanned) with a particular MRI device, it should be planned in advance. This planning includes the selection of the pulse sequence type, and the selection or designation of each parameter in the selected pulse sequence. The selection of such a pulse sequence and its parameterization are in turn based on a number of variables that vary from scan to scan. These variables are related to the particular patient, the type of imaging device, and the particular type and orientation of the magnetic resonance image that is desired. The images obtained are not only related to anatomical features, but also depend on the specific pathological features or suspicious pathological features being studied.

For clinical magnetic resonance scanners, the registration is preset according to the location of the slices, but such registration is not based on the actual position of the patient in the scanner for the particular examination being performed. Typically, these recordings are defined relative to the center of the base field magnet source, which is usually also the origin of the imaging space, with the choice of positive axial, sagittal or coronal slices depending on the preferred recording orientation. In order to perform the actual scan, the final slice position must be adjusted manually, otherwise the slice will not correspond to the intended body region of the examinee. In principle, this manual step has to be performed on a per-record and per-patient basis. This not only prolongs the time the patient has to spend in the scanner, which can be uncomfortable for the patient, but also slows down the examination (i.e. results in fewer patients being scanned in a given amount of time than without such manual positioning quantity).

Usually, this manual readjustment of the slices to the actual scan requires the use of so-called locator records, relative to the slice adjustments of the predefined records. This involves the positioning of the patient in the scanner, the execution of the localizer scan, the localization of slices in the actual diagnostic scan based on the images obtained in the localizer scan and the execution of the clinical or diagnostic scan from which the diagnostic image will be obtained.

In traditional tomographic design content, US Patent No. 6,195,409 introduces the use of templates and PCT application WO 02/43003 describes the use of techniques suitable for tomographic design for medical image processing. The mapping of specific attributes during image processing is disclosed in PCT application WO 02/098292, and the recording of object views is described in PCT application WO 01/59708.

Contents of the invention

An object of the present invention is to provide a method for planning slice positions for tomography surveys, which avoids the artificial slice readjustment described above. Another object of the invention is to provide a method which avoids the use of locator records of the type described previously. This object is achieved according to the principles of the present invention in a slice position planning method for MR (Magnetic Resonance) measurements, where the slices are not planned for each different patient for each scan, but using statistical data sets for specific scans Plan slices, a statistical dataset that describes the geometric details of the organ of interest in the scan. This statistical data set represents a "standard" image of the organ of interest. This data set can be obtained from a standard organ atlas, most of which is known and understandable, or it can be obtained from a data acquisition system by averaging several measurement data sets previously obtained from other patients and stored. produce. Statistical datasets or maps are displayed as planning representations in a global fault localization environment. Measurements (geometric parameters, sequence parameters, etc.) of the imaged region are planned using this statistical data set and stored as standard measurement records for the particular "standard" human organ in question. A standard measurement record includes information about, for example, the position of the imaged region in the data set and the position of the imaged region with respect to a "standard" human organ. The standard survey record also includes information such as the number of slices in the imaging area, the orientation of the slices, the number of pixels per slice, and the size of the pixels. A standard measurement record may allow measurements of a series of imaged regions and/or contain information about saturation regions, etc.

Such standard measurement records can be generated separately for different types of scans, eg for brain scans, pituitary gland scans and functional magnetic resonance (fMRI) scans, epilepsy scans, optic nerve scans or auditory nerve scans.

In order to be able to examine (scan) each patient using a standard measurement record, the record must be adjusted or modified to produce a patient-specific measurement record. For this purpose, the patient's organ to be imaged is positioned in the data acquisition system (scanner) by first low-resolution measurements, for example using a 3D positioner or automatic alignment sequence, followed by geometric mapping of the organ. For this mapping, the geometric relationship of the standard (statistical) organs relative to the patient's organs has to be determined. This can be achieved by comparing templates or by correlation of corresponding datasets. As a result, a transformation matrix is produced which defines how to rotate, translate, zoom in or out the image of the patient's organ in order to map it with the standard organ. The position of the imaging region (slice box) of the standard measurement record is adjusted according to the transformation matrix, which results in a patient-specific measurement record.

A significant advantage of the method according to the invention is that a high degree of reproducibility can be achieved in the inspection. Because the imaging area is automatically determined for each pass starting from the standard imaging area, which is adjusted according to the actual anatomical characteristics of the patient (which usually does not change), the same patient can be scanned multiple times with considerable time intervals in between interval so that individual images scanned at different times can be compared in a meaningful way. This is of great interest when the scan is used to track treatment-specific pathological conditions such as monitoring tumor size during radiotherapy or chemotherapy. When different scans are performed on a patient each time, it is sometimes difficult to compare images from scans because it cannot be reliably determined whether changes in the images detected as a result of the comparison are due to actual changes in tumor size, or because the images The orientation of the slices in one of the images is different from the orientation of the slices in the other images. Due to the high reproducibility achieved by the inventive procedure, when changes are detected between images at different times, those changes which represent actual anatomical changes, rather than changes caused by inconsistent slice positioning, can be more reliably assumed.

A further advantage obtained by the method of the invention is the ability of the imaging device to examine more patients due to the greatly reduced time for planning each tomographic measurement.

Although the method of the present invention has been described above, and will be described in more detail below, in the context of magnetic resonance imaging, the method of the present invention can be applied to any type of tomographic imaging modality, including for example computed tomography and ultrasound imaging.

Description of drawings

Figure 1 is a schematic block diagram of a magnetic resonance imaging apparatus in the form of an exemplary tomography for illustrating the method of the present invention.

Figure 2 is a flowchart of the basic steps for generating a standard measurement record according to the present invention.

Figure 3 shows the basic components or contents of a standard measurement record according to the invention.

FIG. 4 shows the positioning of the tomography box relative to the standard head in a standard measurement record produced according to the invention for a brain scan (brain standard).

FIG. 5 shows the positioning of the tomography box relative to the standard head in a standard measurement record produced according to the invention for a pituitary gland scan (pituitary standard).

FIG. 6 shows the positioning of the tomography cassette relative to the standard head in a standard measurement record produced according to the invention for an fMRI (functional magnetic resonance imaging) scan (fMRI standard).

Figure 7 shows the positioning of the tomography box relative to the standard head in a standard measurement record produced according to the invention for an epilepsy scan (epilepsy standard).

FIG. 8 shows the positioning of the tomography box relative to the standard head in a standard measurement record produced according to the invention for an optic nerve scan (optic nerve standard).

FIG. 9 shows the positioning of the tomogram relative to the standard head in a standard measurement record produced according to the invention for an auditory nerve scan (acoustic nerve standard).

Figure 10 is a flowchart of the method of the present invention for generating a patient-specific measurement record.

11A, 11B and 11C are illustrations for explaining the method of the present invention in FIG. 10 .

Detailed ways

Figure 1 schematically illustrates a magnetic resonance imaging (tomography) apparatus for producing magnetic resonance images of a subject, as an example of a tomography system operable according to the invention. The construction of the magnetic resonance tomography system corresponds to that of a conventional tomography system, but its control takes place according to the invention. The basic field magnet 1 generates a time-constant strong magnetic field for the polarization (calibration) of the nuclear spins in the examination region of the object (for example, a part of the human body to be examined). The high degree of homogeneity of the basic magnetic field required for nuclear magnetic resonance measurements is defined in a spherical measuring space M in which the body part to be examined is placed. To support this uniformity requirement, especially to eliminate time-invariant effects, spacers of ferromagnetic material are placed in place. The influence of time variations is eliminated by the compensating coil 2 driven by the compensating power supply 15 .

A cylindrical gradient coil system 3 is arranged in the basic field magnet 1 , this system 3 comprising 3 secondary coils. Each secondary coil is supplied with current by an amplifier 14 to generate a linear gradient field in each direction of the Cartesian coordinate system. The first secondary coil of the gradient field system 3 produces a gradient G _x in the X-direction, the second secondary coil produces a gradient G _y in the Y-direction, and the third secondary coil produces a gradient G _z in the Z-direction. Each amplifier 14 has a digital-to-analog converter DAC driven by a sequencer 18 for timed generation of gradient pulses.

A radio frequency antenna 4 is located in the gradient field system 3 . The antenna 4 converts the radio frequency pulse sent by the radio frequency power amplifier into an alternating magnetic field, which is used to excite nuclei and make the nuclear spin of the inspection object or the area of the inspection object adjusted to be consistent. The radio frequency antenna 4 is composed of one or more radio frequency transmitting coils and a certain number of radio frequency receiving coils, and these coils are arranged in the form of element coil arrangement (preferably linear arrangement). The alternating field generated from the processing of nuclear spins is also converted into a voltage by the radio-frequency receiving coil of the radio-frequency antenna 4. Here, the nuclear spins are nuclear spins generated by a pulse sequence usually consisting of one or more radio-frequency pulses and one or more gradient pulses. The spin echo signal, and the voltage is provided to the radio frequency receiving channel 8 of the radio frequency system 22 through the amplifier 7 . The radio frequency system 22 also has a transmission channel 9 in which radio frequency pulses are generated to excite magnetic resonance. Based on the pulse sequence of the sequence controller 18 specified by the system computer 20, each radio frequency pulse is digitally represented as a sequence of complex numbers. This digital sequence comprising real and imaginary parts is supplied via respective inputs 12 to a digital-to-analog converter DAC of a radio frequency system 22 and from there to a transmission channel 9 . In the transmission channel 9 the pulse sequence is modulated onto a radio frequency carrier signal which has a fundamental frequency which corresponds to the nuclear spin resonance frequency in the measurement space.

Transmit/receive duplexer 6 for conversion from transmit mode to receive mode. The RF transmitting coil of the RF antenna 4 transmits RF pulses based on the signal from the RF power amplifier 16 to excite the nuclear spins in the measurement space M, and the resulting echo signal is sampled by the RF receiving coil. In the receive channel 8 of the radio frequency system 22 , the obtained NMR signal is phase-sensitively demodulated and converted by a respective analog-to-digital converter ADC into the real and imaginary parts of the measurement signal, which are respectively supplied to the output 11 . The image computer 17 reconstructs an image from the measurement data obtained in this way. Measurement data, image data and control programs are managed by the system computer 20 . On the basis of the control program, the sequence controller 18 monitors the generation of each required pulse sequence and the corresponding k-space sampling. In particular, the sequence controller 18 controls the toothing of the gradient field, the transmission of radio frequency pulses with specific phases and amplitudes, and the reception of nuclear magnetic resonance signals. Timing signals for the radio frequency system 22 and the sequence controller 18 are provided by a synthesizer 19 . The selection of the corresponding control program for generating the nuclear magnetic resonance images and displaying the generated nuclear magnetic resonance images takes place via a terminal 21 having a keyboard and one or more displays.

The method of the present invention can be implemented using the terminal 21 and the system computer 20 . To perform the method represented in the flowchart of FIG. 2, system computer 20 may store therein or access an atlas of anatomical organs. Some such atlases are commercially available and/or accessible online. Such an atlas contains a statistical data set for each of the different anatomical organs.

To plan a scan, an organ atlas or statistical dataset to be imaged in the scan is loaded, accessed or retrieved, and a specific region of interest in the scan is specified. The imaging area is then specified, and the relevant parameters that have been entered are stored together with the atlas reference, which is used to generate a standard measurement record.

The basic content of a standard measurement record for each type of scan carried out according to the flowchart shown in Figure 2 is shown in Figure 3. These components include: the pulse sequence to be used in the scan, the coordinates of the imaged region, and the atlas reference used to generate the recording. As used herein, "reference" means any type of suitable designation, designator or logical link, and a "reference" may be used in a single computer file or folder if all relevant data is contained therein , or associate different files or folders as needed.

The region from which single or multiple slices in the scan are to be obtained is called a "slicebox". In Figures 4-9, the orientation of the tomogram box with respect to the standard head is shown for different standard measurement records produced according to the present invention.

Figure 4 shows the orientation of a brain scan (brain standard) tomogram box relative to a standard head (head atlas). Figure 5 shows the orientation of the tomography box for a pituitary scan (Pituitary Standard). Figure 6 shows the orientation of the tomography cassette for functional magnetic resonance imaging (functional magnetic resonance standard fMRI). In fMRI scans, subjects are periodically stimulated, such as by a flash of light, and brain activity is detected by monitoring the increased oxygen consumption that occurs in the brain, which is caused by the stimulation.

Figure 7 shows the orientation of the tomogram box relative to the standard head in a scan detecting symptoms of epilepsy (epilepsy criteria) in the brain. FIG. 8 shows the orientation of the scan tomogram box (here, as in FIG. 5 , a single slice) at the optic nerve (optic nerve standard), and FIG. 9 shows the orientation of the scan tombox at the auditory nerve (acoustic nerve standard).

The generation of these standard measurement records for different organs according to the invention can be used "independently" or for other purposes. Furthermore, standard measurement records may be used in the method shown in FIG. 10 to generate patient-specific measurement records in accordance with the present invention. As shown in Figure 10, the patient's data set is built through an automated alignment sequence, which represents the patient's actual position in the scanner for a particular exam. Statistical analysis is performed on the patient data set and an appropriate standard measurement record is selected among the standard measurement records generated as described above. This statistical data set (atlas) is then loaded (or accessed or retrieved) and referenced in selected standard measurement records. A transformation matrix is then computed, which provides the mapping between the statistical and patient datasets. The transformation matrix is then applied to transform or translate the standard measurement records into patient-specific measurement records for a particular patient and a particular scan.

The process in the flowchart of Figure 10 continues as shown in Figures 11A, 11B, 11C. The content shown schematically in Figures 11A, 11B, 11C can be displayed visually in the display of the terminal 21 if desired, however, since it is not critical for the operator to actually view these representations, Figures 11A, 11C 11B, 11C can be considered as schematic illustrations of the data processing that takes place in a computer during the implementation of the method of the present invention.

Figure 11A shows a standard head (head atlas) in three different views, and a standard measurement record (SMP) tomogram relative to the standard head. This representation can correspond to any of the examples shown in Figures 4-9 or to standard measurement records for other organs.

Figure 1 IB shows the same views of the head, but these views were obtained from a low resolution scan of the actual patient in the scanning device. The orientation of the organ of interest, in this case the patient's head, will almost certainly differ from the standard head orientation shown in Figure 11A. However, the position of the SMP tomogram shown in each view is the same as that of Fig. 11A. Since the actual position of the patient's head is different from that of the standard head, the SMP tomography cassette will not be properly positioned relative to the actual patient head for performing the desired scan.

In order to restore the proper positioning between the patient head and the tomography box, the transformation matrix described above is generated, which represents the mapping between the standard head and the patient head. The data representing the SMP tomogram in Figure 1 IB is then computed through a transformation matrix, resulting in the transformed tomogram shown in Figure 11C. The positioning of the transformed tomography box relative to the patient head is the same as the positioning of the SMP (Standard Measurement Record) tomography box relative to the standard head.

FIG. 11C thus represents the resulting patient-specific measurement record at the end of the flowchart of FIG. 10 . The actual diagnostic scan is then performed using this patient-specific measurement record.

As noted above, although the process of the present invention has been described in the context of magnetic resonance imaging, it can be used to similar effect in other types of tomography, such as computed tomography and ultrasound imaging.

Although those skilled in the art may suggest modifications and changes, all changes and modifications within the scope of this patent do not depart from the scope of the inventor's contribution to the art.

Claims (26)

1. A method for establishing a standard measurement record for a tomographic imaging system, comprising the steps of: Displays design descriptions of standard objects on a computerized interface with which operators can interact; interacting through the interface with a displayed design description in which a spatial location of a standard tomographic region is defined relative to the standard object; and A standard measurement record is generated and stored, the record including parameters associated with the standard imaging region and a reference specifying the standard object. 2. The method of claim 1, wherein said step of generating and storing said standard measurement record comprises storing parameters defining said spatial location of said standard imaging region. 3. The method according to claim 1, wherein the step of generating and storing a standard measurement record further comprises: in the tomographic imaging system, corresponding to the standard object, including in the standard measurement record Parameters for operating the tomography system to obtain an image of an actual object within the standard image region. 4. The method of claim 1, wherein the tomography system is a magnetic resonance imaging apparatus, and wherein the step of generating and storing a standard measurement record further comprises: in the magnetic resonance imaging apparatus, Corresponding to the standard object, a pulse sequence for the magnetic resonance imaging device to obtain an image of an actual object within the standard image region is specified. 5. The method of claim 1, wherein the standard object is a standard anatomical object, and wherein the step of displaying a design description comprises: displaying the standard anatomical object containing anatomical features of the standard anatomical object design description. 6. The method of claim 5, comprising displaying geometric features of the standard anatomical object as the anatomical features. 7. The method of claim 5, comprising compiling the design description of the standard anatomical object as a statistical average of a plurality of actual objects corresponding to the standard anatomical object. 8. A computer program product comprising a storage medium storing standard measurement records therein, said storage medium being loadable into a computer for controlling the operation of a tomographic imaging device, for said tomographic imaging system, said standard measurement The spatial location of the standard imaging region defining the standard object, and the specified characteristics of the standard object are recorded. 9. The computer program product of claim 8, wherein said standard measurement record contains geometric parameters defining said spatial location of said standard imaging region. 10. The computer program product of claim 8, wherein the specified characteristic of the standard object is an identification of the standard object. 11. The computer program product of claim 8, wherein the characteristic of the standard object includes an identification of an image acquisition system used to generate the standard object. 12. The computer program product of claim 8, wherein said designation comprises a characterization of said standard object selected from the group consisting of anatomical, geometric and statistical features. 13. The computer program product of claim 8, further comprising a designation of a type of tomography system operable using the standard measurement record. 14. The computer program product of claim 8, wherein the standard measurement record further comprises: in the magnetic resonance imaging device, corresponding to the standard object, for operating the magnetic resonance imaging device to obtain The specified pulse sequence for the image of the actual object within the standard image area. 15. A method for planning the positioning of an imaging region in an actual object in a tomographic imaging system, comprising the steps of: placing the real object in the tomography system, and obtaining a data representation characteristic of the real object using the tomography system; generating a computer-usable standard measurement record defining the spatial location of a standard imaging region with respect to a standard object, the standard measurement record referencing a data set characterizing the standard object; In the computer, from the data set characterizing the actual object and the data set characterizing the standard object, the distance between the characteristics of the actual object and the standard object is determined geometric relationship; establishing an actual object-specific measurement record, wherein the imaging region is positioned relative to the actual object by modifying the standard measurement record according to the geometric relationship; Using the object-specific measurement record, an image of the actual object is obtained within the imaging region in the tomography system. 16. The method of claim 15, wherein the actual object is a patient, and wherein the standard object is a standard anatomical object, and wherein the features represented by the respective data sets are anatomical features. 17. The method of claim 15, wherein said step of modifying said standard measurement record to create said object-specific measurement record comprises positioning said imaging region relative to said actual object, relative to said The position of the standard imaging area relative to the standard object is the same. 18. The method of claim 15, comprising defining, in the standard survey record, respective spatial positions for different standard imaging regions with reference to the standard object. 19. The method of claim 18, comprising obtaining different images of the actual object corresponding to the different standard imaging regions using the object-specific measurement records. 20. The method of claim 15, comprising referencing an atlas to obtain said standard object in said standard measurement record. 21. The method of claim 15, comprising generating said standard object in said standard measurement record as a statistical compilation of data from a plurality of actual objects relative to said standard object. 22. The method of claim 21, comprising generating said standard object in said standard measurement record as an average of said plurality of actual objects. 23. The method of claim 15, comprising generating said geometric relationship by associating said data set representing said actual object characteristics and said data set representing said standard object characteristics. 24. The method of claim 15, comprising defining the location and size of the standard imaging region in the standard measurement record. 25. The method of claim 15, comprising defining, in said standard measurement record, the number and thickness of image slices in said standard imaging region. 26. The method of claim 15, wherein the tomography system is a magnetic resonance system, and comprising including a pulse sequence in the standard measurement record for operation using the subject-specific measurement record The magnetic resonance device.

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